Mechanical couplings for joining pipe elements together end-to-end comprise interconnectable segments that are positionable circumferentially surrounding the end portions of co-axially aligned pipe elements. The term “pipe element” is used herein to describe any pipe-like item or component having a pipe-like form. Pipe elements include pipe stock, pipe fittings such as elbows, caps and tees as well as fluid control components such as valves, reducers, strainers, restrictors, pressure regulators and the like.
Each mechanical coupling segment comprises a bridge structure having arcuate surfaces which project radially inwardly and engage plain end pipe elements or circumferential grooves that extend around each of the pipe elements to be joined. Engagement between the arcuate surfaces and the pipe elements provides mechanical restraint to the joint and ensures that the pipe elements remain coupled even under high internal pressure and external forces. The bridge structure defines an annular channel that receives a gasket or seal, typically an elastomeric ring which engages the ends of each pipe element and cooperates with the segments to provide a fluid tight seal.
The segments have connection members positioned at each end, typically in the form of lugs which project outwardly from the bridge structure. The lugs are adapted to receive threaded fasteners, such as nuts and bolts, which are adjustably tightenable to draw the segments toward one another and clamp circumferentially around the ends of the pipe elements.
Considerable torque may be required to tighten the fasteners and effect a fluid-tight seal that has the desired stiffness about the bending and torsional axes of the joint. It is advantageous to take steps to reduce the required fastener torque so that technicians can easily install the couplings in the field manually with hand tools. Reduced required torque also increases battery life when battery powered impact drivers are used to install couplings. The torque reduction is desirable for all types of couplings, and especially for deformable couplings.